1. Field of the Invention
This invention relates to a process for the production of high trans 1,4-polybutadiene. More specifically it relates to a polymerization system using a catalyst comprising a complex of R.sub.2 Mg.
2. Related Prior Art
The most pertinent reference found with regard to catalyst systems comprising complexes of R.sub.2 Mg and ROK is U.S. Pat. No. 3,822,219. This patent is directed primarily to catalytic complexes of dibutyl magnesium with butyl lithium and butyl potassium for the polymerization of olefins, including butadiene, particularly in the presence of a telomerizing agent, such as toluene, to produce low molecular weight polymers or telomers. While most of the discussion and the working examples are directed to the preparation of R.sub.2 Mg.RLi catalyst complexes and their use in preparing telomers, Example XVII (Col. 14) describes the preparation of a complex having the formula (n-C.sub.4 H.sub.9 K).(N-C.sub.4 H.sub.9 MgO-tert-C.sub.4 H.sub.9). This is prepared by reacting 10 moles of potassium tert-butoxide per mole of di-n-butylmagnesium for 5 minutes before butadiene is added.
Either the large excess of t-BuOK or the aging period causes partial replacement of the n-C.sub.4 H.sub.9 from the dibutylmagnesium to give the mixed compound n-C.sub.4 H.sub.9 MgO-t-C.sub.4 H.sub.9 which becomes complexed with the liberated n-C.sub.4 H.sub.9 K. As patentee comments in lines 36-49, this system produces low molecular weight telomers. Furthermore, while the patent is directed mainly to n-BuLi complexes, the maximum trans content shown for the polymer products is the 45% shown in Col. 13, line 16.